In a database management system, when a request to execute a query for inputting/outputting data is received, an execution plan for the query is created, and input/output of data and other processing are executed. In the related art, a query execution plan is generated so as to maximize processing performance under limitations on available computer resources such as a main memory capacity and a secondary memory capacity.
In recent years, there has been a strong demand for reduction of power consumption in addition to improvement of the performance. Thus, an increasing number of storage apparatus have various kinds of power saving functions such as spinning down of a disk drive (refer to Patent Literature 1, Patent Literature 2, Non-Patent Literature 1, and Non-Patent Literature 2).